A.P. Mar'in

New phenomena observed on dissolution of low-molecular compounds in polymers. The sorption isotherms

Abstract The theory of solubility of low-molecular compounds in non-polar polymers is considered. The theory is illustrated with experimental data on additive solubility in polyolefins.

The size distribution of additive sorption centres in polyethylene

Abstract Sorption of various additives by high-density and low-density polyethylenes from hexane and isopropanol has been found to obey the Langmuir sorption law. The concentration of centres participating in sorption of the additive decreases with molecular weight of the latter and the relationship has been established.

New phenomena observed on dissolution of low-molecular compounds in polymers. Antioxidant solubility

Abstract The temperature dependences of antioxidant solubility in polyolefins and in polyamides containing various concentrations of amide groups have been studied. Changes in additive solubility after repeated melting and crystallization of polypropylene were observed. The results are interpreted on the basis of a “two-component” model of the polymeric substance.

Antagonism between phenolic antioxidants and an organic acid

Abstract The role of stearic acid in the kinetics of polypropylene oxidation in the presence of 2,21-methylene-bis(4-methyl-6-tert-butyl-phenol) and 3,5-di-tert-butyl-4-hydroxyphenylpropionic acid diethyleneglycol ester has been studied. It has been demonstrated that this acid increases the critical concentration of the antioxidant with little effect on the rate constant of its consumption. The role of esterification reactions between antioxidant and acid is negligible. It is presumed that oxidant effectiveness is reduced by formation of complexes of antioxidant and acid.

Antioxidant action in polymers: The role of ‘inert’ compounds in inhibited oxidation

Abstract Low-molecular-weight compounds which take no part in polymer oxidation can change the reactivities of other compounds dissolved in the polymer, including antioxidants, by redistributing the antioxidant molecules among the elements of the polymer structure. The effects may be comparable with chemical synergism between antioxidants of different types.

Loss of additives from polyethylene under natural conditions

The loss of antioxidants phenyl-β-naphthylamine and 2,6-di-tert-butyl-4-methylphenol from polyethylene in the open air, in soil and in a water reservoir has been studied. The rates of loss of the antioxidant correspond to the first-order law (−d[A]pdt = k[A]p, where [A]p is the current antioxidant concentration). The role of the environment is discussed.

Temperature dependence of the inhibited oxidation parameters of polyethylene

Abstract Theoretical evaluation of the durability of a stabilized polymer, based on experimental results obtained at elevated temperature or oxygen pressure, is verified for the oxidation of polyethylene.

Retardation of polymer oxidation by natural antioxidant gossypol. Part 1 : kinetics of oxygen consumption

Abstract The kinetics of oxygen consumption in the induction period of oxidation of polypropylene, polyethylene, and polyamide-12 has been studied. It has been shown that the dependence of maximum oxygen consumption rate on concentration is described by a curve with its minimum in the region of low gossypol concentrations. The effectivity of gossypol as an antioxidant is reduced in the polyethylene, polypropylene, and polyamide-12 series.

Antioxidant action in polymers: the limits of non-chemical synergism

Abstract Whilst low concentrations of a relatively inert compound octamethyl-tetrasiloxane increase the antioxidant effect of phenyl-β-naphthylamine in low-density polyethylene melt, the effect disappears at greater concentrations of this additive because the latter changes the polymer structure. The solubility and volatility of phenyl-β-naphthylamine correlate with its antioxidant effectiveness.

Retardation of polymer oxidation by natural antioxidant gossypol: Part 2—Abnormal effects of sulphide and other additives

Abstract The effects of dilauryl thiodipropionate, heptadecane, and phenyl benzoate on polypropylene oxidation in the presence of gossypol have been studied. It has been demonstrated that dilauryl thiodipropionate increases the antioxidant effectiveness of gossypol, provided the latter is used in small concentrations. If gossypol is used in high concentrations its effectiveness is reduced by sulphide. In this case the curves of the dependence of induction period or of oxygen consumption rate on sulphide concentration will show both maxima and minima. It is supposed that these additives exert similar effects on the polymer structure and on the antioxidant distribution in the polymer.